Shale Gas/Oil: The New Frontier Exploration in Brazil

Frederico S. de Miranda
OGX Group

Given the three major geologic models of discoveries in Brazil: the Meso-Cenozoic turbidites in the 1970's and 1980's, the Aptian and Albian carbonates in the 1990's, and more recently the "Pre-Salt" microbial boom in the late 2000's, the unconventional reservoirs have not been focused on by the Brazilian E&P industry so far. Looking through this perspective it is clear that there is a great business opportunity in Brazil, especially for gas-oil shale. Covering 2,680,000 sq km, 31.5% of Brazilian territory, the majority of Paleozoic basins are prolific hydrocarbon producers with well-known petroleum systems. Strategically located in the northern-northeastern region, which is currently undergoing a broad and strong economic growth, and in the southeastern region, an area of scarce energy resources, these basins are major targets for the gas-oil shale model.

With a relatively similar geological evolution, the Paleozoic Paraná, Solimões, Amazonas and Parnaíba basins (the last in development by OGX and MPX partnership) have thick (up to 660 m/2165 ft, with 40 m/130 ft of black shale) Silurian- Devonian shale intervals with a total organic carbon content in the range of 0.1-5% and vitrinite reflectance (Ro) data indicating immature to over mature source rocks, suggesting great potential for gas-oil shale.

Producing since 1937 from conventional reservoirs, the aborted Mesozoic rift basin of Recôncavo also has its own potential, with a thickness of up to 1850 m/6070 ft of lacustrine shales, total organic carbon from 1% to 2% and vitrinite reflectance (Ro) data indicating immature to over mature source rocks that now can be targeted for unconventional reservoirs. In a similar geological context, the onshore portion of Potiguar Basin holds up to 6500 m/21,325 ft of lacustrine shale with TOC up to 4% and vitrinite reflectance (Ro) from immature to mature.

The polycyclic Proterozoic São Francisco Basin has also been the focus of exploration due to several gas seeps registered in the 1980's that are now being associated with shales and tight sands. Lack of public information does precludes further understanding of this play.

The 226 TCF of technically recoverable shale gas resources estimated from the Parana Basin in southwestern Brazil (2011 EIA report) puts these basins and their gas-oil shale scenario in a whole new perspective. However, the absence of shale plays regulation in Brazil needs to be overcome in order to unleash the so far unknown potential of these unconventional reservoirs.

AAPG Search and Discovery Article #90185 © AAPG Geoscience Technology Workshop, Revisiting Reservoir Quality Issues in Unconventional and Conventional Resources, Austin, Texas, November 12-13, 2013